1. Field of the Invention
The present invention relates to a switching mode power supply and a driving method thereof.
2. Description of the Related Art
A switching mode power supply (hereinafter referred to as an “SMPS”) is a device that rectifies an input AC voltage to an input DC voltage (DC-link voltage) and then converts the input DC voltage to an output DC voltage having another level. The output DC voltage can be higher or lower than the input DC voltage. An SMPS is often used in battery powered devices such as power electric devices, mobile phones, and laptop computers.
In general, an SMPS can include a transformer, and has a switching transistor at a primary side of a transformer that receives a DC voltage and controls the duty of the switching transistor. An SMPS can use a feedback loop to transfer a voltage or a current of an output unit to the primary side of the transformer, e.g., through an opto-coupler or through a shunt regulator that is coupled to the output side of the transformer. Application of such a feedback loop allows delivery of a regulated output DC voltage through the output unit.
However, since opto-couplers and shunt regulators are expensive and large, it is difficult to highly integrate an SMPS into circuits and contain cost.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.